Compressor machines with two rotors rotating in opposite directions can operate as compressors or vacuum pumps. EP 1 163 450 A1 discloses a machine of this type, having claw-type rotor blades, which is adapted to generate both suction air and blown air and is particularly suitable for use in the field of paper processing. The internal compression of machines of this type allows to attain markedly higher pressure ratios than for instance by means of a Roots pump. The cantilevered arrangement of the rotors in a pot-shaped housing results in a simple structure. However, the gear that couples the two shafts, on the one hand, and the shaft mounting, on the other hand, are disposed in separate housing parts which need to be exactly aligned with each other and pinned together. Similarly, the pot-shaped housing accommodating the rotors needs to be precisely pinned together with the gear casing. This results in the requirement of having to machine pin holes from two different sides of a housing part as precisely as possible. Any imprecision will lead to slanting shafts and thereby to increased bearing loads, toothed gear noises, and other malfunctions.